Uninterruptible power source apparatus

ABSTRACT

An uninterruptible power supply unit essentially includes: a DC power supply source  3 , a parallel converter  4 , and a series converter  6  that are individually connected in parallel to both ends of an electrolytic capacitor Cdc having a pair of capacitors C 1  and C 2 . An input terminal Pin 1  is connected to an intermediate point of the electrolytic capacitor Cdc. A power supply line  1   n  interlinking an input terminal Pin 1  and an output terminal Pout 2  is connected to multiple switching elements of the parallel converter  4  via a reactor Lin. Likewise, multiple switching elements of the series converter  6  are individually connected to an output terminal Pout 1  via another reactor Lout. Multiple capacitors C individually constituting the above-described reactors L and filters are connected in parallel between the input terminals and output terminals. When any abnormality is generated in the AC input voltage, a controlling device activates operation of the parallel converter  4  so that input current Ipara flowing through the parallel converter  4  can become output current Iout, thereby generating a state equal to the case in which the input side of the AC power supply source has been disconnected from the power supply switch. Concurrently, the controlling device activates operation of the series converter  6  so that the output voltage Vout can become the series-voltage commanding value Vout*.

BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT

The present invention relates to an uninterruptible power supply unitcapable of continuously supplying electric power to a load using energystored in electric power storage means when power service isinterrupted.

As an uninterruptible power supply unit of this type, for example, anuninterruptible power supply unit based on a so-called SPS (stand-bypower supply) system with high operating energy efficiency has beenproposed. FIG. 8 shows an example thereof in which AC power from acommercial power supply source is supplied to a load (not shown) througha relay switch 71. A half-bridge-type converter 72 and a DC power supplysource 73 are-connected to a power supply line for supplying AC input tothe load in parallel relative to an AC power input terminal of the ACpower from the commercial power supply source. Further, a reactor 74 isdisposed between the power supply line and the converter 72. Twoswitching elements connected in series and two capacitors connected inseries, for example, are connected to the converter 72 in parallel.Also, each of the switching elements is connected to a diode in oppositeparallel.

When the AC power is supplied normally, the relay switch 71 iscontrolled in an electrically conductive state to supply the AC input tothe load. On the other hand, when an abnormal condition occurs in the ACinput due to power outage and the like, the relay switch 71 iscontrolled to shut off to disconnect a side of the commercial powersupply from the power supply line. Then, using the DC power supplysource 73 as an energy source, the converter 72 is operated as aninverter to generate specific AC power and supply the AC power to theload.

With the configuration described above, even in the event of poweroutage, AC power can be continuously supplied to the load.

Incidentally, in the SPS-type uninterruptible power supply unitdescribed above, when the SPS system responds and shuts off the relayswitch 71 in the event of power outage, there is a certain time lagabout a few milliseconds to more than 10 milliseconds from a time whenthe power outage is detected to a time when the relay switch 71 is shutoff.

At this time, there may be a case in which the uninterruptible powersupply unit itself or a device linked to the same system may beadversely affected by over current flowing through a short-circuitportion.

Alternatively, in the event of power outage, a method has been proposedin which the converter 72 is temporally stopped to shut off the relayswitch 71, and then the converter 72 is activated again. However, inthis method, since the converter 72 is stopped until the relay switch 71is shut off, there is a problem called “temporal shut off” in which thevoltage output to the load is temporally stopped.

To prevent “temporal shut off”, it is necessary to continuously operatethe converter 72. In this case, however, it is possible to adverselyaffect a device due to the over current described above.

Accordingly, it is desired to provide a device and a method in which theabove two problems are simultaneously solved.

Accordingly, the present invention has been created to solve the aboveproblems, and an object of the present invention is to provide anuninterruptible power supply unit capable of preventing the adverseeffect on a device due to the over current and the temporal shut-off ofthe output voltage when the AC power input side is disconnected upon adecline in the input voltage.

Further objects and advantages of the invention will be apparent fromthe following description of the invention.

SUMMARY OF THE INVENTION

To achieve the above objects, according to a first aspect of the presentinvention, an uninterruptible power supply unit includes a power supplyswitch interposed in a power supply line; a parallel converter disposedbetween the power supply switch and an output terminal of the powersupply line and connected to an input terminal and the output terminalof the power supply line in parallel; an electrically conductive pathdisposed between said power supply switch and said parallel converterfor connecting between the power supply lines; electric power storagemeans connected to said parallel converter; a series converter connectedto said power supply line disposed between said parallel converter andsaid output terminal in series for adjusting said AC output voltageusing said electric power storage means as an energy source so that theAC output voltage at said output terminal becomes a predetermined value;voltage abnormality detection means for detecting an abnormality in theinput voltage of the AC power supplied to said input terminal; andcontrolling means for controlling an operation of said power supplyswitch and said parallel converter in response to a result detected bysaid voltage abnormality detection means; wherein said controlling meanscontrols said power supply switch to be conductive, and also controlssaid parallel converter so that the energy stored in said electric powerstorage means becomes a predetermined voltage value when said voltageabnormality detection means detects no abnormality; and said controllingmeans shuts off said power supply switch and controls said parallelconverter so that a value of a current flowing through said parallelconverter matches a value of an AC output current at said outputterminal when said voltage abnormality detection means detects anabnormality.

In the first aspect of the present invention, when an abnormality of theinput voltage of AC power is not detected, the input AC power is outputto the load as it is. At this time, the series converter connected tothe power supply line in series adjusts the AC output voltage at theoutput terminal to be a predetermined value, and the AC output voltageis output to the load. When the energy stored in the electric powerstorage means is varied due to the voltage adjusting operation of theseries converter, the parallel converter connected to the power supplyline in parallel is operated to adjust the energy stored in the storagemeans to be a predetermined value, thereby maintaining the energy storedin the storage means at the predetermined value.

On the other hand, when an abnormality is detected in the input voltageof AC power due to power outage and the like, the power supply switch iscontrolled to shut off and the parallel converter is operated to matchthe value of the AC current flowing through the parallel converter tothe value of the AC output current at the output terminal, that is, theinput current of the AC power becomes zero. Accordingly, at the timewhen the parallel converter starts controlling to make the input currentzero before the power supply switch is shut off, the input side of theAC power comes to a state equal to being disconnected from the powersupply line. Further, the series converter is operated so that the ACoutput voltage becomes a predetermined value, so that a temporalshut-off does not occur in the event of power outage and a predeterminedvoltage value of the AC output voltage is output.

According to a second aspect, an uninterruptible power supply unitincludes a power supply switch interposed in a power supply line; aparallel converter disposed between the power supply switch and anoutput terminal of the power supply line and connected to an inputterminal and the output terminal of the power supply line in parallel;an electrically conductive path disposed between said power supplyswitch and said parallel converter for connecting between the powersupply lines; electric power storage means connected to said parallelconverter; an input reactor disposed between said input terminal of saidpower supply line and said parallel converter; a series converterconnected to said power supply line disposed between said parallelconverter and said output terminal in series for adjusting said ACoutput voltage using said electric power storage means as an energysource so that the AC output voltage at said output terminal becomes apredetermined value; voltage abnormality detection means for detectingan abnormality in the input voltage of the AC power supplied to saidinput terminal; and controlling means for controlling an operation ofsaid power supply switch and said parallel converter in response to aresult detected by said voltage abnormality detection means. Thecontrolling means controls said power supply switch to be conductive,and also controls said parallel converter so that the energy stored insaid electric power storage means becomes a predetermined voltage valuewhen said voltage abnormality detection means detects no abnormality,and the controlling means shuts off said power supply switch andcontrols said parallel converter so that a value of the AC input currentat said input terminal becomes lower than a predetermined allowablevalue when said voltage abnormality detection means detects anabnormality.

According to a third aspect of the present invention, in theuninterruptible power supply unit, said controlling means controls theparallel converter so that the value of said AC input current becomeszero when said voltage abnormality detection means detects anabnormality.

In the second or third aspect, when no abnormality is detected in theinput voltage of AC power, the input AC power is output. At this time,the series converter connected to the power supply line in seriesadjusts the AC output voltage so that the AC output voltage at theoutput terminal becomes a predetermined value and is output. As aresult, a predetermined value of voltage is output to the load to whichthe uninterruptible power supply unit supplies the power. When theenergy stored in the electric power storage means is varied by thevoltage-adjusting operation executed by the series converter, theparallel converter connected to the power supply line in parallel isoperated to adjust the energy stored in the electric power storage meansto be a predetermined value, thereby maintaining the energy stored inthe storage means at a predetermined value.

On the other hand, when an abnormality is detected in the input voltageof the AC power, the power supply switch is shut off and the value ofthe AC input current at the input terminal is controlled to be below apredetermined allowable value, such as zero. Accordingly, at the timewhen the parallel converter starts controlling to make the input currentzero before the power supply switch is shut off, the input side of theAC power is in a state equal to being disconnected from the power supplyline. Further, the series converter is operated so that the AC outputvoltage becomes a predetermined value of the AC output voltage, so thata temporal shut-off does not occur in the event of power outage and theAC power with a predetermined voltage value of the AC output voltage isoutput continuously.

The above-mentioned allowable value is not limited to zero, and, forexample, a current value is acceptable in which no adverse effect occurson the uninterruptible power supply unit itself or a device connected tothe uninterruptible power supply unit due to a current flowing through ashort circuit portion when a short circuit and the like happens.

According to a fourth aspect of the present invention, in theuninterruptible power supply unit, the controlling means controls theparallel converter using a voltage at both ends of the electricallyconductive path as an opposite voltage for improving control precisionrelative to the parallel converter. Also, electrically conductive pathabnormality detection means is provided for detecting an abnormality inthe voltage at both ends of the electrically conductive path, so thatwhen the electrically conductive path abnormality detection meansdetects an abnormality in the voltage at both ends of the electricallyconductive path, a predetermined rated voltage is used as the oppositevoltage.

According to a fifth aspect the present invention, in theuninterruptible power supply unit, the predetermined rated voltage isset to be a value so that the voltage at both ends of the electricallyconductive path can be a specific value within a compensating voltagerange of the series converter when an abnormality occurs in the voltageat both ends of the conductive path.

According to a sixth aspect of the present invention, in theuninterruptible power supply unit, the preset predetermined voltage iszero voltage.

In the fourth to sixth aspects, the controlling means controls theparallel converter using a voltage at both ends of the electricallyconductive path between the power supply lines disposed between thepower supply switch and the parallel converter as the opposite voltagefor improving the control precision relative to the parallel converter.In other words, the parallel converter is controlled based on theopposite voltage and a controlling signal for controlling such that theenergy stored in the electric power storage means becomes a rated value.Since the controlling signal for controlling such that the energy storedin the electric power storage means becomes a rated value is very smallrelative to the opposite voltage, the controlling signal is controlledto be the opposite voltage.

Here, when an abnormality occurs in the input voltage and the input sideof the AC power is opened, the voltage output of the parallel converteris detected as the voltage at both ends of the electrically conductivepath. That is, since the parallel converter is controlled such that theoutput voltage is a target value, the output voltage of the parallelconverter is maintained at a substantially constant value.

Accordingly, when the substantially constant value exceeds a range thatthe series converter can compensate, the series converter can not adjustthe AC output voltage to be a predetermined value at the outputterminal, thereby decreasing voltage. However, when an abnormalityoccurs in the input voltage, since the output voltage from the parallelconverter is set to be a value at which the series converter can becompensated to be a predetermined value, i.e. zero, as the oppositevoltage, the series converter can be compensated to be the predeterminedvalue, thereby maintaining the AC output voltage at a predeterminedvalue.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic block diagram showing an example of anuninterruptible power supply unit according to a first embodiment of thepresent invention;

FIG. 2 is a block diagram showing a functional structure of a parallelconverter controlling unit shown in FIG. 1;

FIG. 3 is a schematic block diagram showing a functional structure of aseries converter controlling unit;

FIG. 4 is a schematic block diagram showing an example of anuninterruptible power supply unit according to a second embodiment ofthe present invention;

FIG. 5 is a schematic block diagram showing a functional structure of aparallel converter controlling unit shown in FIG. 4;

FIG. 6 is a schematic block diagram showing a functional structure of aparallel converter controlling unit according to a third embodiment ofthe present invention;

FIG. 7 is a schematic block diagram showing a functional structure of aparallel converter controlling unit according to a further embodiment ofthe present invention; and

FIG. 8 is a circuit diagram showing an example of a conventionaluninterruptible power supply unit.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Hereunder, embodiments of the present invention will be explained.

First, a first embodiment of the present invention is described below.

FIG. 1 is a schematic circuit diagram showing an example of anuninterruptible power supply unit according to the first embodiment ofthe present invention. As shown in FIG. 1, in the uninterruptible powersupply unit, AC input from a commercial power supply source is suppliedto a load (not shown) through a relay switch 10. The uninterruptiblepower supply unit comprises an electrolytic capacitor Cdc; a parallelconverter 4 for charging and discharging the electrolytic capacitor Cdc;and a series converter 6 for adjusting a voltage so that an outputvoltage Vout to the load becomes an output voltage target value Vout*with the electrolytic capacitor Cdc and a DC power supply source 3 as aenergy source.

The parallel converter 4 is formed of a half-bridge circuit, and a diodeD1 and a diode D2 are connected to a switching element SW1 and aswitching element SW2 connected together in series in opposite parallel,respectively. Likewise, the series converter 6 is formed of ahalf-bridge circuit, and a diode D3 and a diode D4 are connected to aswitching element SW3 and a switching element SW4 connected together inseries in opposite parallel, respectively.

A DC power supply source 3, the parallel converter 4, and the seriesconverter 6 are connected in parallel in this order to both ends of theelectrolytic capacitor Cdc comprising a capacitor C1 and a capacitor C2with same storage capacity connected in series. A middle point and oneinput terminal Pin1 of the electrolytic capacitor Cdc are connected viathe relay switch 10. One end of the reactor Lin is connected to aconnection point of the switching elements SW1 and SW2 of the parallelconverter 4, and the other end is connected to a power supply line 101connecting the other input terminal Pin2 and an output terminal Pout2.

Further, a capacitor Cin is connected to the input terminals Pin1 andPin2 in parallel at connection points between the relay switch 10 andthe electrolytic capacitor Cdc, and between the input terminal Pin2 andthe reactor Lin of the power supply line 101. The capacitor Cin and thereactor Lin constitute an LC filter 2.

A connection point of the switching elements SW3 and SW4 of the seriesconverter 6 is connected to an output terminal Pout1 through a reactorLout. A capacitor Cout is connected to the output terminals Pout1 andPout2 in parallel at connection points between the reactor Lout and theoutput terminal Pout1, and between the reactor Lin and the outputterminal Pout2 of the power supply line 101. The capacitor Cout and thereactor Lout constitute an LC filter 8.

It is arranged that a controlling circuit 20 controls the parallelconverter 4, the series converter 6, and the relay switch 10.

The controlling circuit 20 comprises a parallel converter controllingunit 22 for controlling the parallel converter 4, a series convertercontrolling unit 24 for controlling the series converter 6, and a switchcontrolling unit 26 for controlling the relay switch 10.

FIG. 2 is a schematic block diagram showing a functional structure ofthe parallel converter controlling unit 22. As shown in FIG. 2, anarithmetic operator 41 detects a differential value between a specifiedDC voltage value Edc* as a target value of a voltage at both ends of theelectrolytic capacitor Cdc and a DC-voltage Edc at both ends of theelectrolytic capacitor Cdc detected by a charged voltage detector 33. Avoltage adjuster 42 executes a voltage-adjusting arithmetic operationsuch as PI control, and an arithmetic operator 43 multiplies a result ofthe arithmetic operation and a reference sine wave signal sin ωt.Incidentally, the reference sine wave signal sin ωt is a signal with aphase synchronized with a inter-line voltage V_(L), and an amplitude ofthe reference sine wave signal is arbitrarily determined, for example,in correspondence with a rated voltage of an input voltage Vin from acommercial power supply source.

A changeover switch 44 selects one of the multiplication result at thearithmetic operator 43 and a value of the output current Iout, and thenthe selected data is output to an arithmetic operator 45. A differentialvalue is obtained by subtracting a current component Ipara (hereinafterreferred to as parallel converter current) flowing through the parallelconverter 4 detected by a parallel converter current detector 35 fromone of a multiplication result at the arithmetic operator 43 and theoutput current Iout selected by the changeover switch 44, and thedifferential value is then output to a current adjuster 46. The currentadjuster 46 executes a current adjust arithmetic operation such that acurrent value corresponding to the differential value between thespecified DC voltage value Edc* and the DC voltage Edc matches thecurrent value of the parallel converter current Ipara, or the currentvalue of the parallel converter current Ipara matches the output currentvalue Iout, and an executed result is input to an arithmetic operator47. The inter-line voltage V_(L) detected by an inter-line voltagedetector 37 a is input to the arithmetic operator 47 as an oppositevoltage for improving control precision relative to the parallelconverter, and a differential value between an executed result at thecurrent adjuster 46 and the inter-line voltage V_(L) is obtained.

Based on the executed result at the arithmetic operator 47, a PWMcontrolling unit 48 generates a pulse signal. At this time, the parallelconverter 4 performs a rectifying operation, and a pulse signal isgenerated such that the parallel converter current Ipara becomes aspecific current value corresponding to the differential value betweenthe specified DC voltage value Edc* and the DC voltage Edc, or theparallel converter current Ipara becomes a real time value of the outputcurrent Iout. The pulse signal is then output as a signal forcontrolling the switching element SW1 of the parallel converter 4 and,at the same time, a logical-inversion circuit 49 inverts a PWM signal sothat the inverted signal is output to control the switching element SW2.

The changeover switch 44 is controlled to output an output of thearithmetic operator 43 to the arithmetic operator 45 when the inputvoltage Vin detected by the input-voltage detector 37 is within apredetermined allowable range where the input voltage is considered tobe normal. The changeover switch 44 is controlled to output a value ofthe output current Iout detected by the output-current/voltage detector31 to the arithmetic operator 45 when the input voltage Vin exceeds theallowable range, i.e. above or below the allowable range.

That is, when the input voltage Vin is normal, the parallel convertercontrolling unit 22 controls the parallel converter 4 to operate as aPWM rectifier, and controls the parallel converter 4 through feedingback the parallel converter current Ipara so that the current flowingthrough the parallel converter 4, i.e. the parallel converter currentIpara, becomes a value corresponding to the differential value betweenthe specified DC voltage value Edc* and the DC voltage Edc. On the otherhand, when the input voltage Vin is an abnormal voltage, the parallelconverter 4 is controlled so that the parallel converter current Iparamatches a value of the output current Iout.

FIG. 3 is a block diagram showing a functional structure of the seriesconverter controlling unit 24. As shown in FIG. 3, an arithmeticoperator 51 detects a differential value between the output voltage Voutdetected by the output-current/voltage detector 31 and the specifiedvalue Vout* of the output voltage to the load. After a voltage adjuster52 executes PI control and the like based on the differential value, aPWM controlling unit 53 generates a pulse signal as a control signal forcontrolling the switching element SW3 of the series converter 6 and, atthe same time, a logical inversion circuit 54 inverts the pulse signalas a control signal for controlling the switching element SW4, therebyperforming the PWM control of the switching elements SW3 and SW4.

With this configuration, the series converter 6 is controlled throughfeedback so that the output voltage Vout becomes the specified outputvoltage value Vout*.

When the input voltage Vin detected by the input-voltage detector 37 iswithin a predetermined allowable range where the input voltage Vin isconsidered to be normal, the switch controlling unit 26 controls therelay switch 10 to be electrically conductive, and when the inputvoltage Vin exceeds the predetermined allowable range, the relay switchis controlled to be in the shut-off state.

An operation of the first embodiment will be explained next.

When an input voltage from a commercial power supply source is normal,since the input voltage Vin detected by the input-voltage detector 37 iswithin a predetermined allowable range, the controlling circuit 20determines that the input voltage Vin from a commercial power supplysource is normal. Accordingly, the switch controlling unit 26 controlsthe relay switch 10 to be in the electrically conductive state. As aresult, the AC power supplied from a commercial power supply source issupplied to the load (not shown) through the relay switch 10, the LCfilter 2, the series converter 6, and the LC filter 8.

At this time, the series converter 6 compensates the input voltage Vinso that the output voltage Vout becomes the specified output voltagevalue Vout* using the electrolytic capacitor Cdc and the DC power supplysource 3 as an energy source, and the compensated input voltage issupplied to the load via the LC filter 8. As a result, the AC power witha specific voltage value corresponding to the specified output voltagevalue Vout* is supplied to the load.

On the other hand, in the parallel converter controlling unit 22, thechange-over switch 44 selects a side of the arithmetic operator 43 toinput the output thereof to the arithmetic operator 45, and the parallelconverter 4 performs a rectifying operation so that a currentcorresponding to the differential value between the specified DC voltagevalue Edc* and the DC voltage Edc flows through the parallel converter4. Accordingly, when the series converter 6 compensates the outputvoltage Vout using the electrolytic capacitor Cdc and the DC powersupply source 3 as the energy source, and the voltage at both ends ofthe electrolytic capacitor Cdc varies, the parallel converter 4 isoperated so that the specified DC voltage value Edc* matches the DCvoltage Edc.

That is, even if the voltage at both ends of the electrolytic capacitorCdc varies when the series converter 6 compensates the output voltageVout, the voltage at both ends of the electrolytic capacitor Cdc ismaintained at the specified DC voltage value Edc* since the parallelconverter 4 charges and discharges into and out from the electrolyticcapacitor Cdc.

From this state, if a short circuit occurs on the input side of the ACpower supply source and the value of the input voltage Vin exceeds apredetermined allowable range, the input voltage Vin decreases and thecontrolling circuit 20 determines that the input voltage Vin is anabnormal voltage. The series converter controlling unit 24 continuouslycontrols the series converter 6 as before, and the series converter 6 isoperated so that the output voltage Vout matches the specified outputvoltage value Vout*. Also, the switch controlling unit 26 controls therelay switch 10 to be in the shut off state.

On the other hand, in the parallel converter controlling unit 22, sincethe decrease in the input voltage Vin is detected, the parallelconverter 4 is controlled using the value of the output current Ioutdetected by the output-current/voltage detector 31 as the specifiedvalue of the current flowing through the parallel converter 4 throughthe change-over switch 44.

Here, when the abnormal voltage of the input voltage Vin is detected andthe relay switch 10 is controlled to be in the shut-off condition, ittakes time from when the relay switch 10 is actually shut off to whenthe input side of the AC power supply source is disconnected. However,at the moment when the abnormal voltage of the input voltage Vin isdetected, in the parallel converter controlling unit 22, the parallelconverter 4 is controlled so that the current flowing through theparallel converter 4 becomes the value of the output current Iout, thatis, the input current value becomes zero. This is an equivalent statebefore the relay switch 10 is in the shut off condition, that is, thestate in which the input side of the AC power supply source is shut offat the moment when the abnormal voltage of the input voltage Vin isdetected.

Accordingly, this is an equivalent state in which the input side of theAC power supply source is promptly disconnected at the moment when theabnormal voltage of the input voltage Vin is detected. Therefore, it ispossible to prevent an adverse effect on the uninterruptible powersupply unit itself or a device linked with the same system due to anover current flowing at a short-circuit portion, thereby improvingreliability.

Also, since the series converter 6 is operated so that the outputvoltage Vout becomes the specified output voltage value Vout*, it ispossible to prevent temporal shut-off of the output voltage Vout to theload and continuously supply the AC power with a voltage valuecorresponding to the specified output voltage value Vout*.

A second embodiment of the present invention will be explained next.

FIG. 4 is a schematic block diagram showing an example of anuninterruptible power supply unit according to the second embodiment ofthe present invention. According to the second embodiment, instead ofthe reactor Lin in the first embodiment, an input reactor 11 is disposedbetween a connection portion of the capacitor Cin of the power supplyline 101 and a connection portion between the switching elements SW1 andSW2 of the power supply line 101, and the capacitor Cin and the inputreactor 11 constitute the LC filter 2 a. Further, a reactor Lout′ isdisposed between a connection portion of the capacitor Cout of the powersupply line 101 and a connection portion between the switching elementsSW1 and SW2 of the power supply line 101, and the reactors Lout, Lout′and the capacitor Cout constitute a filtering circuit 8 a.

The switch controlling unit 26 and the series converter controlling unit24 control the relay switch 10 and the series converter 6, respectively,as in the first embodiment of the present invention, and a parallelconverter controlling unit 22 a controls the parallel converter 4. Notethat components same as those in the first embodiment are designated bythe same reference numerals and symbols, and detailed descriptionsthereof are omitted.

The parallel converter controlling unit 22 a in the second embodiment isconstituted as a block diagram shown in FIG. 5.

As shown in FIG. 5, an arithmetic operator 51 detects a differentialvalue between the DC-voltage Edc at both ends of the electrolyticcapacitor Cdc detected by the charged voltage detector 33 and thespecified DC voltage value Edc* thereof. A voltage adjuster 52 executesa voltage-adjusting arithmetic operation such as PI control, and anarithmetic operator 53 multiplies a result of the arithmetic operationand the reference sine wave signal sin ωt. Incidentally, the referencesine wave signal sin ωt is a signal with a phase synchronized with ainter-line voltage V_(L), and an amplitude of the reference sine wavesignal is arbitrarily determined, for example, in correspondence withthe rated voltage of the input voltage from a commercial power supplysource.

A result of the multiplication at the arithmetic operator 53 and acommanding value of “0” is selectively output to an arithmetic operator55 through a change-over switch 54. The arithmetic operator 55 computesa differential value between the result obtained at the arithmeticoperator 53 or the commanding value “0” selectively input and an inputcurrent Iin flowing through an input reactor 11 detected by an inputcurrent/voltage detector 38. A current adjuster 56 executes a currentadjusting operation so that the differential value becomes zero, and anarithmetic operator 57 computes a differential value between the resultcomputed by the current adjuster 56 and the inter-line voltage V_(L)detected by an inter-line voltage detector 37 a.

Based on the computed result, a PWM controlling unit 58 generates apulse signal for controlling the parallel converter 4. At this time, theparallel converter 4 performs a rectifying operation, and a pulse signalis generated so that the input current Iin matches a current valuecorresponding to the differential value between the specified DC voltagevalue Edc* and the DC voltage Edc, or the input current Iin becomeszero. The pulse signal is output as a signal for controlling theswitching element SW1 of the parallel converter 4 and, at the same time,a logical inversion circuit 59 inverts the pulse signal and the invertedsignal is output as a signal for controlling the switching element SW2.

When the input voltage Vin detected by the input current/voltagedetector 38 is within a predetermined allowable range where the inputvoltage Vin is considered to be normal, the change-over switch 54outputs the result computed by the arithmetic operator 53 to thearithmetic operator 55, and when the input voltage Vin exceeds thepredetermined allowable range, the changeover switch 54 outputs thecommanding value “0” to the arithmetic operator 55.

That is, when the input voltage Vin is normal, the parallel convertercontrolling unit 22 a controls the parallel converter 4 so that theinput current Iin matches a current value corresponding to thedifferential value between the specified DC voltage value Edc* and theDC voltage Edc. Conversely, when the input voltage Vin is abnormal, theparallel converter 4 is controlled so that the input current Iin becomeszero. Incidentally, the input current Iin is not necessary to be zero,and a small current value relative to the rated current applied to theuninterruptible power supply unit shown in FIG. 4 may be acceptable,i.e. a current value small enough so that there is no adverse effect onthe uninterruptible power supply unit and a device linked to the samesystem due to a current flowing upon power outage at the input side ofthe AC power supply source. It is preferred to be “0” in view ofreliability.

An operation of the second embodiment will be explained next.

When an input voltage from a commercial power supply source is normal,since the input voltage Vin detected by the input-voltage detector 38 iswithin a predetermined allowable range, the controlling circuit 20determines that the input voltage Vin is normal. Accordingly, the switchcontrolling unit 26 controls the relay switch 10 to be in theelectrically conductive state. As a result, the AC power supplied from acommercial power supply source is supplied to the load (not shown)through the relay switch 10, the LC filter 2, the series converter 6,and the LC filter 8. At this time, the series converter 6 compensatesthe input voltage from a commercial power supply source so that theoutput voltage Vout becomes the specified output voltage value Vout*using the electrolytic capacitor Cdc and the DC power supply source 3 asan energy source, and the output voltage is supplied to the load via theLC filter 8. As a result, the AC power with a specific voltage valuecorresponding to the specified output voltage value Vout* is supplied tothe load regardless of the voltage value of the AC input.

On the other hand, in the parallel converter controlling unit 22 a, thechange-over switch 54 selects a side of the arithmetic operator 53 toinput the output thereof to the arithmetic operator 55. Accordingly, theparallel converter 4 performs a rectifying operation with a currentcorresponding to the differential value between the specified DC voltagevalue Edc* and the DC voltage Edc as a target value of the input currentIin. When the series converter 6 compensates the output voltage Voutusing the electrolytic capacitor Cdc and the DC power supply source 3 asthe energy source, and the voltage at both ends of the electrolyticcapacitor Cdc varies, the parallel converter 4 is operated with thecurrent corresponding to the differential value between the specified DCvoltage value Edc* match the DC voltage Edc as the target value of theinput current Iin.

Accordingly, even if the voltage at both ends of the electrolyticcapacitor Cdc varies when the series converter 6 compensates the outputvoltage Vout, the voltage at both ends of the electrolytic capacitor Cdcis maintained at the specified DC voltage value Edc* since the parallelconverter 4 charges and discharges into and out from the electrolyticcapacitor Cdc.

From this state, if a short circuit occurs at the input side of the ACpower supply source and the value of the input voltage Vin exceeds apredetermined allowable range, the input voltage Vin decreases and thecontrolling circuit 20 determines that the input voltage Vin is anabnormal voltage. The series converter controlling unit 24 continuouslycontrols the series converter 6 as before, and the series converter 6 isoperated so that the output voltage Vout matches the specified outputvoltage value Vout*.

On the other hand, in the parallel converter controlling unit 22 a,since the decline of the input voltage Vin is detected, the parallelconverter 4 is controlled with the commanding value “0” as a specifiedvalue of the input current Iin through the change-over switch 54.

Here, when the abnormal voltage of the input voltage Vin is detected andthe relay switch 10 is controlled to be in the shut-off condition, ittakes time until the relay switch 10 is in the shut off state and theinput side of the AC power supply source is disconnected. However, atthe moment when the abnormal voltage of the input voltage Vin isdetected, in the parallel converter controlling unit 22, the parallelconverter 4 is controlled so that the input current Iin becomes zero.This is an equivalent state before the relay switch 10 is in a shut offcondition, i.e. the state in which the input side of the AC power supplysource is shut off at the moment when the abnormal voltage of the inputvoltage Vin is detected.

Accordingly, when short circuit and the like happens, it is possible toprevent an adverse effect on the uninterruptible power supply unititself or a device linked with the same system due to an over currentflowing at a short-circuit portion, thereby improving reliability.

At this time, since the series converter 6 is operated so that theoutput voltage Vout becomes the specified output voltage value Vout*using the electrolytic capacitor Cdc and the DC power supply source 3 asthe energy source, the AC power with a voltage value corresponding tothe specified output voltage value Vout* is continuously supplied to theload, and it is possible to prevent temporal shut-off of the outputvoltage Vout.

In the first and second embodiments, it is stated that the parallelconverter 4 and the series converter 6 are respectively formed of ahalf-bridge circuit comprising the switching elements and diodesconnected in opposite parallel, however, the present invention is notlimited thereto, and a full-bridge may be applicable.

In the first and second embodiments, the relay switch 10 corresponds toa power supply switch; the parallel converter 4 corresponds to aparallel converter; the electrolytic capacitor Cdc and the DC powersupply source 3 correspond to electricity storage means; the seriesconverter 6 and the series converter controlling unit 24 correspond to aseries converter; the input-voltage detector 37 or the inputcurrent/voltage detector 38 corresponds to voltage abnormality detectionmeans; the switch controlling unit 26 and the parallel convertercontrolling unit 22 or 22 a correspond to controlling means; and theinput reactor 11 corresponds to an input reactor.

A third embodiment of the present invention will be explained next.

According to the third embodiment, in the first embodiment, allcomponents are the same except that the parallel converter controllingunit 22 has a different configuration, and the same components aredesignated by the same reference numerals and descriptions thereof areomitted.

As shown in FIG. 6, in the parallel converter controlling unit 22 of thefirst embodiment shown in FIG. 2, the parallel converter controllingunit 22 of the third embodiment further includes a PLL circuit 61 and alimiter circuit 62.

The PLL circuit 61 inputs the inter-line voltage V_(L) detected by theinter-line voltage detector 37 a, so that the reference sine wave signalsin ωt having a phase synchronized with that of the inter-line voltageV_(L) is generated and input to the arithmetic operator 43.

As shown in FIG. 6, the limiter circuit 62 comprises a comparator 71 forcomparing the inter-line voltage V_(L) with the reference value “0” [V];a comparator 72 for comparing the reference sine wave signal sin ωt fromthe PLL circuit 61 with the reference value “0”; an EOR circuit 73 forreceiving outputs from the comparators 71 and 72 as inputs and foroutputting an exclusive sum thereof; a NOT circuit 74 for invertingoutput of the EOR circuit 73; and an arithmetic operator 75 formultiplying the input voltage Vin and output of the NOT circuit 74 sothat output of the arithmetic operator 75 is output to the arithmeticoperator 47.

The comparator 71 compares the inter-line voltage V_(L) with thereference value “0” [V], and when the value of the inter-line voltageV_(L) is greater than the reference value “0”, the comparator 71 outputsa logical value “1”, and when the value of the inter-line voltage V_(L)is less than the reference value “0”, the comparator 71 outputs alogical value “0”. The comparator 72 compares the reference sine wavesignal sin ωt with the reference value “0”, and when the value of thereference sine wave signal sin ωt is greater than the reference value“0”, the comparator 72 outputs the logical value “1”, and when the valueof the reference sine wave signal sin ωt is less than the referencevalue “0”, the comparator 72 outputs the logical value “0”.

That is, when a sign of the inter-line voltage V_(L) matches a sign ofthe reference sine wave signal sin ωt, the NOT circuit 74 outputs thelogical value “1”, and when they do not match, the NOT circuit 74outputs the logical value “0”. Since one of them is multiplied by theinter-line voltage V_(L), when the sign of the inter-line voltage V_(L)matches the sign of the reference sine wave signal sin ωt, theinter-line voltage V_(L) is input to the arithmetic operator 47, andwhen they do not match, “0” is input.

The arithmetic operator 47 makes the output of the arithmetic operator75 an opposite voltage for changing control characteristics in theparallel converter controlling unit 22 relative to the parallelconverter 4, and a differential value between the opposite voltage andthe output of the current adjuster 46 is obtained and output to the PWMcontrolling unit 48, so that a pulse signal to the parallel converter 4is generated based on the value.

Accordingly, in the third embodiment, when the input voltage Vin from acommercial power supply source is normal and the relay switch 10 iscontrolled to be in the conductive state, the input voltage Vin isdetected as the inter-line voltage V_(L), and the sign thereof matchesthe sign of the reference sine wave signal sin ωt from the PLL circuit61. Accordingly, the inter-line voltage V_(L) is input to the arithmeticoperator 47 as the opposite voltage, and an operation is similar to thatof the first embodiment.

On the other hand, when a short circuit occurs at the input side of theAC power supply source and the input voltage Vin exceeds a predeterminedallowable range, the input voltage Vin decreases and the controllingcircuit 20 determines that the input voltage Vin is an abnormal voltage.The parallel converter 4 is controlled with the value of the outputcurrent Iout detected by the output-current/voltage detector 31 as thecommanding value of the current flowing through the parallel converter 4through the change-over switch 44, and the relay switch 10 is controlledto be in the shut off state.

With this operation, the state is equivalent to that before the relayswitch 10 is fully shut off, i.e. the state that the input side of theAC power supply source is disconnected at the moment when theabnormality of the input voltage Vin is detected.

Here, when the input voltage Vin is in the normal state, the parallelconverter controlling unit 22 executes a control operation with a sum ofthe differential value between the specified DC voltage value Edc* andthe DC voltage Edc, a output voltage of the current adjuster 46corresponding to the difference from the parallel converter currentIpara, and the inter-line voltage V_(L), i.e. the input voltage Vin, asthe opposite voltage, as the commanding value of the PWM controllingunit 48. At this time, since an adjustable voltage for controlling thecurrent corresponding to the voltage output from the current adjuster 46is negligible, the output voltage of the parallel converter 4 issubstantially equal to the opposite voltage, i.e. the inter-line voltageV_(L).

From this state, when the input side of the AC power supply source iscut off, the output voltage of the parallel converter 4 is detected asthe inter-line voltage V_(L), and is input to the arithmetic operator 47as the opposite voltage. Accordingly, in the parallel convertercontrolling unit 22, the output voltage of the parallel converter 4 isdetected and the parallel converter 4 is controlled to output a voltageequivalent to the detected voltage, so that the output voltage ismaintained at a constant voltage.

Here, the series converter 6 is operated such that the output voltageVout matches the specified output voltage value Vout*. However, in thestate that the input side of the AC power supply source is disconnected,since the output voltage of the parallel converter 4 is detected as theoutput voltage Vout, the series converter 6 executes a compensatingoperation so that the output voltage Vout maintained at a substantiallyconstant voltage becomes the AC specified output voltage value Vout*.Accordingly, in a case that the output voltage Vout, i.e. the outputvoltage of the parallel converter 4 maintained at a substantiallyconstant level, is within a voltage compensation range of the seriesconverter 6, the series converter 6 is enabled to compensate the valueto be the specified output voltage value Vout*. However, in a case thatthe output voltage of the parallel converter 4 exceeds the voltagecompensation range of the series converter 6, it is no longer possibleto satisfy the specified output voltage value Vout*, thereby decreasingthe output voltage. That is, for example, when the voltage compensationrange of the series converter 6 is set to be 0 to ±100% and the outputvoltage of the parallel converter 4 is maintained at a value at thepositive (+) side, for example, X [V], since it is not possible tocompensate toward the negative (−) side, the output voltage Voutdecreases.

However, in the limiter circuit 62, it is compared whether the detectedinter-line voltage V_(L) and the reference sine wave signal sin ωtsynchronized with the inter-line voltage V_(L) have the same sign. Asdescribed above, when the input side of the AC power supply source isdisconnected and the voltage output of the parallel converter 4 becomesa substantially constant voltage, the output voltage is detected as theinter-line voltage V_(L). Since the signs of the reference sine wavesignal sin ωt and the inter-line voltage V_(L) do not match, zerovoltage is output to the arithmetic operator 47 as the opposite voltage.

Accordingly, in the parallel converter controlling unit 22, the parallelconverter 4 is controlled with the voltage adjustment for controllingthe current output from the current adjuster 46 as the commanding value.However, since the voltage-adjustment for controlling the current isnegligible, the output voltage of the parallel converter 4 becomessubstantially zero, and the series converter 6 is operated to output thespecified output voltage value Vout*.

Accordingly, when the voltage compensation range of the series converter6 is set to be 0 to ±100%, since the output voltage of the parallelconverter 4 is within the voltage compensation range, in the seriesconverter 6, is it possible to compensate the output voltage to the loadto be the specified output voltage value Vout*.

Accordingly, it is possible to prevent the output voltage Vout fromdeclining, and even when an abnormal condition happens at the input sideof the AC power supply source, it is possible to supply the power stablywithout temporal shut out or disconnection.

In the third embodiment described above, it is stated that the PLLcircuit 61 and the limiter circuit 62 are added to the parallelconverter controlling unit 22 a in the first embodiment. This is alsoapplicable to the second embodiment.

In this case, as shown in FIG. 7, in the parallel converter controllingunit 22 a shown in FIG. 5, the PLL circuit 61 and the limiter circuit 62are added. When the sign of the inter-line voltage VL matches the signof the reference sine wave signal sin ωt, the inter-line voltage VL isoutput to the arithmetic operator 57 as the opposite voltage, and whenthe sign of the inter-line voltage VL does not match the sign of thereference sine wave signal sin ωt, voltage 0 is output to the arithmeticoperator 57 as the opposite voltage.

Accordingly, in this case, as described above, when the input side ofthe AC power supply source is disconnected, the output voltage of theparallel converter 4 is detected as the inter-line voltage V_(L), andthe detected voltage is output to the arithmetic operator 47 as theopposite voltage, so that the output voltage of the parallel converter 4is maintained at a substantially constant voltage. At a moment when thesubstantially constant voltage is detected as the inter-line voltageV_(L) and the sign of the reference sine wave signal sin ωt does notmatch the sign of the inter-line voltage VL, zero voltage is output tothe arithmetic operator 47 as the opposite voltage.

Accordingly, the output voltage of the parallel converter 4 becomessubstantially zero, and the series converter 6 is capable of correctingthe output voltage to be the specified output voltage value Vout*, sothat the output voltage Vout to the load is maintained at the specifiedoutput voltage value Vout*. Accordingly, even when an abnormal conditionhappens at the input side of the AC power supply source, it is possibleto supply the power stably without temporal shut out or disconnection.

Incidentally, in the third embodiment, it is stated that when anabnormality happens at the input side of the AC power supply source, thevoltage 0 is input as the opposite voltage. However, it is not limitedthereto, and it is set according to the compensation range of the seriesconverter 6. In short, when the input side of the AC power supply sourceis disconnected, the appropriate opposite voltage is set such that theoutput voltage of the parallel converter 4 becomes a specific value thatthe series converter 6 can maintain the output voltage Vout to the loadat the predetermined specified output voltage value Vout*.

In the third embodiment, it is stated that the limiter circuit 62switches the opposite voltage to the arithmetic operator 47. However, itis not limited thereto, and it is possible to apply switching means forswitching the corresponding voltage value to the zero voltage upon thedetection when the opposite voltage is abnormal, i.e. the output voltageof the parallel converter 4 is varied due to a change in the oppositevoltage, and the value becomes such that the series converter 6 can notmaintain the output voltage Vout at the specified output voltage valueVout*.

As described above, according to the uninterruptible power supply unitof the first to third aspects of the present invention, when the ACinput voltage is abnormal, the parallel converter is operated such thatthe value of the current flowing through the parallel converter becomesthe value of the AC output current and the value of the AC input currentbecomes zero, or the parallel converter is operated such that the valueof the AC input current become less than a predetermined allowable valuesuch as zero, for example, thereby creating the state equivalent to thestate in which the input side of the AC power supply source isdisconnected. As a result, in the case that the power supply switch isshut off upon the detection of an abnormal voltage of the AC input andthe parallel converter is controlled so that the value of the AC inputcurrent becomes zero, it is possible to make the input side of the ACpower supply source the state equivalent to the state that the inputside of the AC power supply source is disconnected at the moment whenthe parallel converter starts controlling to make the value of the ACinput current zero before the power supply switch is shut off. With thisconfiguration, it is possible to prevent the adverse effect on theuninterruptible power supply unit itself or a device linked to the samesystem due to over current flowing at a short-circuit portion, therebyimproving reliability.

Further, at this time, since the series converter is operated such thatthe AC output voltage becomes the commanding value, it is possible tocontinuously supply the AC output at a specific voltage value andprevent the temporal shut out state.

In the uninterruptible power supply unit of the fourth to sixth aspects,the parallel converter is operated with the voltage at both ends of theconductive path connecting between the power supply lines disposedbetween the power supply switch and the parallel converter as theopposite voltage. When an abnormality happens in the voltage at bothends of the conductive path, the rated voltage is used as the oppositevoltage in place of the voltage at both ends of the conductive path. Therated voltage is set to be a value such as zero so that the seriesconverter can correct the output voltage of the parallel converter, i.e.the AC output voltage at the output terminal, to be a predeterminedvalue while the power supply switch is shut off. Accordingly, it ispossible to continuously supply the AC output with a predeterminedvoltage value, and prevent the temporal shut out.

1. An uninterruptible power supply unit for receiving AC power input andsupplying AC power output, comprising: a power supply line including afirst power supply line having first input and output terminals, and asecond power supply line having second input and output terminals, apower supply switch interposed in the first power supply line forconnecting and disconnecting the first power supply line, a parallelconverter connected between the power supply switch and the first outputterminal parallel to the first and second input and output terminals, aconductive path for connecting the first and second power supply linesbetween the power supply switch and the parallel converter, electricalpower storage means connected to the parallel converter for storingelectrical power, a series converter connected to the first power supplyline in series between the parallel converter and the first outputterminal for maintaining a voltage of the AC power output at the firstoutput terminal at a predetermined value using the electrical powerstorage means as an energy source, voltage abnormality detection meansconnected to the first and second input terminals for detecting anabnormality of the AC power input at the first and second inputterminals, and controlling means connected to the power supply switch,the parallel converter and the voltage abnormality detection means forcontrolling the power supply switch and the parallel converter inresponse to a result detected by the voltage abnormality detectionmeans, said controlling means, when the voltage abnormality detectionmeans detects no abnormality, controlling the power supply switch toconnect the first power supply line and controlling the parallelconverter so that the electrical energy stored in the electrical powerstorage means has a predetermined value, and when the voltageabnormality detection means detects the abnormality, controlling thepower supply switch to disconnect the first power supply lines and theparallel converter.
 2. An uninterruptible power supply unit according toclaim 1, wherein when the voltage abnormality detection means detectsthe abnormality, said controlling means controls the parallel converterso that a value of a current flowing through the parallel convertermatches a value of a current of the AC power output at the first outputterminal.
 3. An uninterruptible power supply unit according to claim 1,further comprising an input reactor disposed between the second inputterminal and the parallel converter.
 4. An uninterruptible power supplyunit according to claim 3, wherein when the voltage abnormalitydetection means detects the abnormality, said controlling means controlsthe parallel converter so that an input current value of the AC inputpower at the first input terminal is lower than a predetermined value.5. An uninterruptible power supply unit according to claim 4, whereinwhen the voltage abnormality detection means detects the abnormality,said controlling means controls the parallel converter so that a valueof a current of the AC power input at the first input terminal becomeszero.
 6. An uninterruptible power supply unit according to claim 1,further comprising conductive path voltage abnormality detection meansconnected to two ends of the conductive path for detecting anabnormality in a voltage therebetween, said controlling meanscontrolling the parallel converter using the voltage at the two ends ofthe conductive path as an opposite voltage for improving controlprecision relative to the parallel converter, said controlling means,when the conductive path abnormality detection means detects theabnormality, controlling the parallel converter using a predeterminedrated voltage as the opposite voltage.
 7. An uninterruptible powersupply unit according to claim 6, wherein said rated voltage is set tobe a value so that the voltage at the two ends of the conductive pathwhen the conductive path abnormality detection means detects theabnormality is within a voltage range such that the series converter cancompensate.
 8. An uninterruptible power supply unit according to claim6, wherein said rated voltage is zero voltage.